1. Field of the Invention
The present invention relates to a controller of a work piece-conveying robot for controlling the motion of a robot in supplying an unprocessed work piece to a machine tool or taking out a processed work piece from a machine tool.
2. Description of Related Art
In general, in a processing system using a robot comprising a numerically controlled machine tool and a robot provided with a robot hand for carrying out at least one of supplying and taking-out of a work piece to and from the numerically controlled machine tool, when a robot teaching operation is performed, a position is usually taught to the robot while a robot hand is being moved in a manual jog feed. In the manual jog feed of the robot hand, when the robot hand is in a specified working area, for example in a working area above a table for a work piece to be fixed in the machine tool, the teaching operation is simplified by performing the manual jog feed using a coordinate system that is parallel to the table in this working area, so that the coordinate system parallel to the table is often adopted as a manual jog feed coordinate system in this working area. There are one or more manual jog feed coordinate systems stored in a robot controller and distinguished by the number given to the respective coordinate system or by comments added to the coordinate system in order to be able to select and utilize a suitable one. When the robot teaching operation is to be performed, a manual jog feed coordinate system suitable to the working area in which the robot hand exists is selected, and is switched to other manual jog feed coordinate system as robot hand is moved to different working area. Switching of the coordinate system is performed by an operator who inputs the number of the appropriate coordinate system to be used via a teaching operation panel into a robot controller based on an identification information such as the number or the comments.
An example of conventional robot control method related to the present invention is known from the disclosure of Japanese Unexamined Patent Publication No. 03-37701 (JP-A-03-37701). In Japanese Unexamined Patent Publication No. 03-37701, from the lowermost line at lower right column of page 2 to the 7th line from the bottom at upper left column of page 3, there is a description that “process 1 in which a servo controller is caused to store the designated operating area that is inputted by an operator in a working coordinate system designated on the basis of a reference coordinate system, process 2 in which the angle of the arm joint is detected for each sampling period, and the position of the hand tip is determined from the detected angle of the arm joint, process 3 in which it is determined, for each sampling period, whether or not the position of the hand tip of the robot is included in the designated operating area, and if it is determined that the position is included in the designated operating area, process 4 in which a command in accordance with the processing level set for the designated operating area is sent to the servo controller to control the motion of the robot, and if it is determined that the position is not included in the designated operating area, the teaching operation or the working operation of the robot is continued so as to repeat the procedure from process 2 to process 3”.
Also, from the lines 2 to 10 of the lower right column of page 5, there is a description that “at the position of the tip of a robot hand while carrying out the teaching operation or working in a job, a monitoring area or a movement limiting area can be easily set at an arbitrary position as required by an operator freely in a plural orthogonal coordinate systems such that, when it is detected that the position of hand tip has entered into the designated operation area, the command signal in accordance with a preset processing level can be given to control the robot motion. Thus, advantageously, operability of the robot can be thereby improved, and safety can be assured against wrong motion of the robot”.
In the conventional method, while the robot hand is being moved in manual jog feed in the robot teaching operation, an operator was required to switch the manual jog feed coordinate system to be used in accordance with the working area for carrying out the teaching operation, and the operator had to select and determine a suitable manual jog feed coordinate system each time from the number or the added comment of the manual jog feed coordinate systems stored in the controller. If the operator fails to switch the manual jog feed coordinate system and continues to use the manual jog feed coordinate system unsuitable to the working area to carry out the jog feed in the teaching operation, not only the motion of moving the robot hand in manual jog feed becomes complicated, but it may become sometimes necessary to go several points back to a teaching point and to switch the manual jog feed coordinate system and to do the manual jog feed operation over again. If, in switching the manual jog feed coordinate system, a wrong manual jog feed coordinate system is selected, the robot hand may be moved in the manual jog feed in an undesired direction or to an undesired position.